Chapter 12-13: Type 2 Diabetes Mellitus (DM)

TEXTBOOK PRESENTATION

Patients with type 2 DM can have the classic symptoms of poly­uria, polydipsia, and weight loss. The presentation can also be more subtle, with patients complaining that they feel tired or “just not right.” Many patients are asymptomatic; the diagnosis is made after plasma glucose testing. The complications of diabetes may already be present by the time patients seek medical attention.

DISEASE HIGHLIGHTS

1. Caused by a combination of impaired insulin secretion and insulin resistance with no evidence of autoimmunity

2. Accounts for 90–95% of cases of DM, with prevalence in the United States of about 9.4%, with considerable variation by ethnic group

   1. The prevalence in American Indian/Alaska Native persons is 15.1%.

   2. The prevalence in black and Hispanic persons is 12–14%.

   3. The prevalence in Asian, non-Hispanic persons is 8%, with Asian Indians having the highest prevalence (11.2%).

   4. The prevalence in white, non-Hispanic persons is 7.4%.

3. Diabetes is undiagnosed in 24% of people.

4. Strong genetic component

   1. 39% of patients have at least 1 parent with diabetes

   2. 60–90% concordance in monozygotic twins

   3. The lifetime risk of a first-degree relative of a patient with type 2 DM is 5–10 times higher than that of age- and weight-matched individuals without a family history.

5. The most important risk factor is obesity, which induces insulin resistance.

   1. The relative risk of diabetes developing in a woman who has a body mass index (BMI) > 35 kg/m² is 93, compared with a woman who has a BMI < 22 kg/m².

   2. The relative risk of diabetes developing in a man who has a BMI > 35 kg/m² is 42, compared with a man who has a BMI < 23 kg/m².

6. DKA develops less often in patients with type 2 DM than those with type 1; however, DKA can occur in persons with type 2 DM. Recent data show that two-thirds of patients with DKA have type 1 DM, and one-third have type 2 DM.

   Do not assume all patients with DKA have type 1 DM; DKA can develop in persons with type 2 DM.

7. Risk factors for type 2 DM include

   1. Age ≥ 45

   2. BMI ≥ 25 kg/m²

   3. A first-degree relative with diabetes

   4. Physical inactivity

   5. Being a member of a high-risk ethnic group (African American, Latino, Native American, Asian American, Pacific Islander)

   6. Having delivered a baby weighing > 9 pounds or having had gestational DM

   7. Hypertension

   8. High-density lipoprotein (HDL) cholesterol < 35 mg/dL or triglycerides > 250 mg/dL

   9. Polycystic ovary syndrome

   10. Vascular disease

   11. Prediabetes (impaired glucose tolerance [IGT], impaired fasting glucose [IFG], or mildly elevated HbA_1c; see Evidence-Based Diagnosis section for definitions)

       1. Patients with either IGT or IFG have a 5–10% annual risk of developing diabetes; those with both have a 10–15% annual risk.

       2. Patients with an HbA_1c in the prediabetes range have an annual risk of 10–50% with the risk increasing as the HbA_1c increases.

       3. These annual risks are 10–20 times higher than in people ...